1. Field of the Invention
This invention relates to an upsetter for upsetting end portions of elongated work member of steel and like materials, and more particular to a clamp mechanism for an upsetter which is capable of clamping work members securely to prevent sliding deviations of work members in dies when an upsetting force is applied or when associated punches are withdrawn after upsetting operation, gripping individual works separately in a simultaneous upsetting operation of a plurality of work members no matter whether the work members contain variations in outside diameter (e.g., owing to a large tolerance).
2. Description of the Prior Art
Known upsetters for upsetting ends of lengthy work members are largely classified as a vertical type which has vertically split dies as illustrated in FIGS. 1 and 2 and a horizontal type which has horizontally split dies as illustrated in FIG. 3.
As seen in FIGS. 1 and 2, the vertical type upsetter is provided with vertically split dies 1 and 2 which are opened and closed in a horizontal direction by a drive mechanism which is provided at one side of the machine. The upsetter is provided with a U-shaped frame 3 which is open on the upper side and supports on its inner side the above-mentioned dies 1 and 2. In order to prevent the frame 3 from being expanded on the upper open side at the time of gripping work members 4, a cross tie rod 5 is provided perpendicularly along the upper side of the frame 3. Therefore, in the vertical type upsetter with the dies 1 and 2 enclosed on four sides as seen in the direction of arrow II of FIG. 2, there invariably arises the necessity for transferring the work members 4 along a relatively long path of travel to deliver the same to the front side of the machine and for moving the work in the longitudinal directions when inserting and extracting it before and after the upsetting operation.
More specifically, as seen in FIGS. 1 and 2, a work member 4 which has its end portion heated in a furnace 6 is transferred horizontally over a certain distance for delivery to the working position of the upsetter as indicated by arrow I and then moved in the longitudinal direction for insertion into the upsetter as indicated by arrow II. The work member 4 which is inserted in the upsetter is then lowered stepwise as indicated by arrow III to undergo the primary and secondary upsetting operations in the dies 1 and 2. Upon completion of the upsetting operation, the work member 4 is drawn out of the upsetter by moving the same longitudinally backward over a substantial distance as indicated by arrow IV and then lifted to the initial level as indicated by arrow V, followed by a horizontal movement over a large distance as indicated by arrow VI for transfer to the location of the next operation.
Consequently, the forming operation by a vertical upsetter entails the transfer of the heated or upset work member 4 in horizontal directions as indicated by arrows I and VI within a short time period in addition to large longitudinal movements in the directions of arrows II and V. Namely, it entails the drawback that it requires complicated and costly transfer and handling mechanisms for moving the work member in lateral, longitudinal and vertical directions. Besides, there has to be provided a long path of transfer in total to cope with the large breadth of the upsetter including the drive mechanism provided at one side thereof, and the transfer of works in three different directions, resulting in a prolonged time for one cycle of operation, lower productivity and high production cost.
Especially, in the case of hot forging, the work members cool off while moved along the long path of transfer, so that greater force and energy are required for the upsetting operation and the number of consecutive operations which are possible per one heating is limited. Consequently, due to the difficulty of completing the forming operation with only one heating stage, there arise the necessities for die replacement and reheating of the works before finishing the upsetting operation.
In order to eliminate these drawbacks, there has been developed a horizontal type upsetter which, as seen in FIG. 3, is provided with horizontally split dies 8 and 9 in a horizontal row. The dies 8 and 9 and opened and closed vertically by a drive mechanism which is located over the dies 8 and 9.
As shown in FIG. 3, in the horizontal type upsetter, work members which are passed horizontally through part of the split dies 8 and 9 are moved back and forth to avoid the interference of paired pull rods 11 which serve to maintain the gripping force of the dies 8 and 9. That is, the work members which are fed into the machine in a slightly retracted position to dodge the pull rod 11 are pushed in and they are fed transversely to undergo sequentially the primary and secondary upsetting operations in the dies 8 and 9, respectively. Upon finishing the upsetting, the work members are retracted again to avoid interference of the other pull rod 11 before they are discharged from the upsetter for transfer to the location of the next operation.
The horizontal type upsetting machine which has a smaller width needs a shorter path of travel and thus contributes to shortening the cycle time of the upsetting operation and enhances the productivity as compared with the vertical type. Another advantage of the horizontal type upsetter resides in the fact that the transfer and handling mechanisms can be simplified to a significant degree as the main transfer routes are all in the same horizontal plane. Further, in contrast to the vertical type the dies of which are enclosed by a frame on four sides, the horizontal type upsetter permits observation of the conditions of upset products from three sides when the dies are opened and accordingly it has an advantage that some suitable measures can be taken promptly to remove the cause of a defect as soon as a defective product comes out.
Although the path of travel of work members in the horizontal upsetter is two-dimensional, that is to say, on one horizontal plane, the work members have to be moved in the longitudinal directions to evade collision with the pull rods 11 which move only a small distance in the longitudinal direction. Namely, there still remains the problem of complicated transfer or feed mechanism in the known horizontal upsetter which is not constructed to transfer the works or products along a linear path.
Further, the clamp mechanism in either type of the above-described conventional upsetter is usually provided with unitary die holders 14 and 15 on die plates 16 and 17 for holding in juxtaposed position upper and lower clamp dies 12 and 13, respectively, as seen in FIG. 16 which exemplifies a horizontal type upsetter, pressing the upper dies and die holders by a hydraulic cylider 19 which is provided in a tong head 18 integrally with the upper die plate 16. Therefore, in the particular example shown, when a couple of tubes which contain variations in outside diameter are simultaneously clamped, one clamp die which receives a tube of a smaller diameter fails to grip it securely against skidding forces upon the thrust of punches 20 in the upsetting stage, making the simultaneous upsetting of the two tubes impossible.
Such a clamping failure leads to drop in product quality and to difficulty in performing the upsetting operation itself especially in the case of oil well tubes which have a relatively large tolerance in the outside diameter as compared with other steel workpieces and which are formed in a broad range of various outside diameters, for example, in the range of 30 mm to 270 mm. In addition, the clamp mechanism of the conventional upsetter employs a hydraulic cylinder 19 of a predetermined capacity so that it has been difficult to increase the clamping force and thus to change the clamping power of the upsetter to a higher required level.